Cathode dampener



Aug. 6, 15957 B. D. MAGERS CATHODE DAMPENER Filed Feb. a, 1956 KNVENTORBERNARD D. MAGERS ATTORNEY P 2,802,132 Patented A g- CATHODE DAMIPENERBernard D. Magers, Shawnee, 0kla., assignor to Sylvania ElectricProducts Inc., acorporatiorr of. Massachusetts Application February 8.,19.56,.SeriaINo. $564,191

6 Claims. (Cl. 313-261) and anode usually have prolongations extendingthrough the insulators and fastened thereto by some means. The cathodecannot be so fastened since it is subject to thermal expansion.Therefore it is usually mounted in one of the insulators in such amanner that it cannot move longitudinally relative thereto, and mountedfor free movement in the other of the insulators. However, this freedomof movement in the other insulator may be such as to allow lateralmovement of the cathode thereby varying the. spacing between cathodeandgrid. and upsetting the electrical characteristics of the device.This is particularly true after repeated heating and cooling of thecathode with consequent wear on the adjacent walls of the insulator.

It is an object of the invention to provide a means for firmlysupporting the otherwise free end of a cathode to prevent lateralmovement of the cathode while yet permitting longitudinal expansionthereof.

It is another object of the invention to so construct this supportingmeans that there shall be no freedom of motion of said cathode withrespect to the support means even after repeated expanding andcontracting movements of the cathode.

It is yet another object of the invention to provide a simple means forpositioning the cathode and which will operate efiiciently for the lifeof the electron device even though subjected to the high temperatureconditions existing within the tube during manufacture and subsequentnormal use.

As an exemplification of the invention and a better understandingthereof, attention is directed to the following specification andaccompanying drawings in which Fig. 1 is a vertical elevation of anelectron tube showing the electrode mount in cross section.

Fig. 2 is a similar view but showing, in exaggerated degree, theappearance of the upper support for the cathode when the cathode iselongated due to being heated.

Fig. 3 is a top view of the electron mount, and

Fig. 4 is a side view of the tube illustrated in Figs. 1 to 3 taken atright angles to Fig. 1.

Referring to the drawings in greater detail, at there is disclosed anenvelope within which is a mount 12, in this instance comprising aduo-triode, one triode being comprised of an anode 14, grid 16 andindirectly heated cathode 18, and the second triode comprising anode 20,grid 22 and cathode 24, all suitably connected to pin terminalsextending through the base of the envelope. The electrode elements areall held in proper spaced relationship to each other by top insulatingwafer 26 and bottom insulating wafer 28. These wafers are here shown asof conventional material, namely mica, the wafers being provided withtriangular teeth 30 frictionally engaging the inner-walls of theenvelope. The anodes. arev fixed in-position between the micas 26. and.28 by twisting end tabs 32 and.34, respectively, .on the top and bottomedges of'the anodes, .as is conventional in the art, connection tothetube terminal pins from the anodes being-effected by directly weldingselected ones of these pins to end tabs of the anode and which extendthrough the lower mica. The grid is. held in place. by frictionalcontact of the grid side. rods with both of the micas or by. welding togrid stops (not shown) fastened to the micas, as is customary in theart. Also the. terminal pins, as pin'36, may be made of a height to abutthe lower face of the lower micaand when welded to the grid side rod,the construction will effect a. rigid mounting ofthe grid and the lowermica Within the envelope. The cathode sleeves are held in place withinthe envelope in a novel manner. Each cathodesleeve is usually providedwith a head 38 near one.v end of the sleeve. The sleeves are inserted in.aperturesain, thelower mica 28, until the bead rests on sion of .thecathode sleeves on heating thereof, without buckling of thesleeve andwithout exerting strain on the micas. However, if the loose fit of theupper ends of the; cathode were the only means of support for thecathodes, the tube could easily prove to be microphonic andwould haveother undesirable physical and electrical characteristics, as. may beeasily. perceived. To steady the cathode sleeves. and yet allow forexpansion thereof, the-upper ends of'the sleeves are supported by aresilient support or bridge 40 made of mica. This material has apositive coeificient of expansion and unlike metal springs will not loseits resilient characteristics when subjected to heat. The cathodesleeves snugly engage perforations in said bridge and are furtherfastened thereto by crimping and flaring the upper ends of the sleevesover the upper face of the mica bridge as shown at 42. The bridge 40 isa narrow strip of mica with pointed teeth 44 similar to the teeth 30,these teeth frictionally engaging the inner walls of the tube andproviding pivots for the bridge on expansion and fiexure thereof, butyet permit some sliding motion of the bridge along the axis of the gridside rods. The siderods of the grids 16 and 22 pass loosely throughapertures 46 in the mica whereby no forces are imposed on the gridsthrough bridge fiexure use, but the side rods do prevent unduerotational movement of the bridge in a plane normal to the grid siderods. The anode is not secured to the bridge, since it is secured to thetop mica outside of the narrow bridge. In Fig. 3 conventional slots 48in the upper mica are shown, these being provided to reduce leakageacross the face of the mica. To maintain these slots open, the bridge 40may be provided with recessed portions 50, registering with the slots48.

In Figs. 1, 3 and 4, the bridge 40 is shown in its position when thecathode sleeve is not heated. In Fig. 2, the bridge is shown in a flexedposition to illustrate how the cathode sleeve can expand, when heated,without injury to the electron device. The degree of fiexure is greatlyexaggerated for the sake of clarity.

Having thus described the invention, what is claimed as new is:

1. In an electron device, an envelope, a pair of spaced insulatingmembers therein engaging interior walls of the envelope and supportingelectrode elements therebetween, one of said elements being anindirectly heated cathode, said cathode fitting snugly in one of saidmembers and loosely in the other, and an additional resilient spacingmember adjacent said other member also engaging walls of the envelope,said additional member being fixedly secured to the cathode and free formovement at its junction with the cathode toward and away from saidother member.

2. In an electron device, an envelope, a pair of spaced insulatingmembers therein engaging interior walls of the envelope and supportingelectrode elements therebetween, one of said elements being anindirectly heated cathode, said cathode fitting snugly in one of themembers and loosely in the other, and an additional resilient spacingmember, normally lying close to said other member, fixedly secured tothe otherwise loosely supported end of the cathode, said additionalspacing member having portions engaging opposite interior walls of theenvelope and being free from attachment with said other spacing member.

3. In an electron device, an envelope, a pair of spaced insulatingmembers therein engaging interior walls of the envelope and supportingelectrode elements therebetween, one of said elements being anindirectly heated cathode, said cathodefitting snugly in one of themembers and loosely in the other, and a mica bridge normally lying closeto said other member, fixedly secured to the otherwise loosely supportedend of the cathode, said mica bridge having portions engaging oppositeinterior walls of the envelope and being free from attachment with saidother spacing member.

4. In an electron device, an envelope, a pair of spaced insulatingmembers therein engaging interior walls of the envelope and supportingelectrode elements therebetween including an anode, a grid and acathode, means for securing the anode and grid to said spacing membersto prevent movement therebetween, means for securing the cathode to oneof said members to prevent relative movement therebetween, said cathodepassing freely through said other member, a resilient third spacingmember adjacent said other member also engaging interior walls of 4 Vthe envelope and fastened to the otherwise free 'end of the cathode,said grid having side rods extending through said other member andloosely through perforations in the third spacing member.

5. In an electron device, an envelope, a pair of spaced insulatingmembers therein engaging interior walls of the envelope and supportingelectrode elements therebetween including an anode, a grid and acathode, means for securing the anode and grid to said spacing membersto prevent movement therebetween, means for securing the cathode to oneof said members to prevent relative movement therebetween, said cathodepassing freely through said other member, a third sheet mica spacingmember adjacent said other member also engaging interior walls of theenvelope and fastened to the otherwise free end of the cathode, saidgrid having side rods extending through said other member and looselythrough perforations in the third sheet mica spacing member.

6. In an electron device, an envelope, a pair of spaced insulatingmembers therein engaging interior walls of the envelope and supportingelectrode elements therebetween,

References Cited in the file of this patent UNITED STATES PATENTSGronros Aug. 8, 1950 Zorgman Nov. 4, 1952

